1. Field of the Invention
The present invention relates to rupture disks, and more particularly to an improved rupture disk having a generally circular score pattern which cuts at least halfway through the disk material using a beveled cut.
2. General Background
Rupture disks are used for the relief of pressure from process vessels and the like. Such vessels are typically expensive so that a failure of the vessel can create significant property damage, the threat of personal injury or death, as well as environmental hazard. Rupture disks are commercially available in a variety of sizes, shapes, and with various pressure values.
Several patents have issued on rupture disks.
U.S. Pat. No. 3,484,817 discloses a safety pressure relief valve in the form of a reverse buckling disc having a cross hair pattern.
U.S. Pat. No. 3,520,443 issued to R. M. Selby discloses a safety vent structure that includes a cross hair pattern that divides the disc into six pie-wedge shaped segments.
In U.S. Pat. No. 3,704,807 issued to Robert Lidgard there is provided a pre-bulged, frangible member and a relief device employing the frangible member that has a predetermined burst pattern that is relieved into its crown which insures that no portion of the member is severed from the member when it fails. The basic pattern uses radial slits extending from the periphery of the crown and terminating short of the center. The center portion of the crown is relieved with a pattern employing at least one non-rupturable interconnecting web between the apex and the remainder of the member so that upon failure this web remains the apex of the crown.
The Dernbach, et al U.S. Pat. No. 3,845,879 dicloses a safety fitting for a pipe or vessel and contained within a flange coupling. The device includes a rupture disc with radial grooves placed on one side which will normally be at a higher pressure and is backed by a perforated support member placed on the other side such that under normal conditions the support member supports the rupture disc in the areas of the grooves. If the pressure on the other side exceeds that on the one side of the disc is no longer supported and will rupture allowing flow through the fitting.
A quick opening rupture disc is seen in the Taylor U.S. Pat. No. 3,257,026. The device includes a circular disc having a cross hair pattern.
The Coffman U.S. Pat. No. 2,980,286 entitled "Safety Pressure Relief Device Support" discloses a rupture disc of generally concave convex shape having an annular generally circular skirt at its periphery with a central concave convex disc portion.
The Porter U.S. Pat. No. 3,121,509 entitled "Damage Resistant Rupture Disc Assembly" provides a concave convex disc-shaped member having an arcuate slot that tracks a generally circular path but terminates at two end portions to provide a hinge there between.
In the Raidl U.S. Pat. No. 3,722,734 entitled "Safety Relief Device" there is provided a burst pattern that is cut or relieved in the dome of the disc to fail at a pressure less than the snapover pressure so that pressure causing snapover results in failure and bursting of the disc. The apparatus includes a frangible disc and support assembly that includes a ceiling diaphragm member and a support member. The support member has a circular slit which extends a substantial distance around the base portion of the dome. A second support member is provided on the downstream side of the support member to overlay the relieved portion and thus prevent it from premature failure.
A Shear diagram relief union is the subject of U.S. Pat. No. 2,553,267. The 267 patent is provides a circular relief device having a diaphragm or web connected to a ring and has a generally circular groove adjacent to its connection with the ring except for a short portion which serves as a hinge when the diaphragm shears.
The Fike U.S. Pat. No. 2,716,506 entitled "Rupture Disc Assembly for High Pressure Vessels" provides a diaphragm providing an arcuate slot in the diaphragm and preferring that the slot be substantially larger than a semicircle so that the member will swing away in hinge-like manner substantially clear of the relief opening.
Presently, under current manufacturing methods, the lowest burst pressure obtainable for a scored, tension-loaded rupture disk is about 70 psig at about 72.degree. Fahrenheit in a one-inch size. This type of disk is manufactured by using a mechanical score blade to cut more than halfway through the disk material in a "cross hair" score configuration. However, the "cross hair" score configuration is not practical in small sizes such as, for example, less than one inch.